One of the important factors limiting solar-cell efficiency is that incident photons generate one electron-hole pair, irrespective of the photon energy. Any excess photon energy is lost as heat. The ...possible generation of multiple charge carriers per photon (carrier multiplication) is therefore of great interest for future solar cells. Carrier multiplication is known to occur in bulk semiconductors, but has been thought to be enhanced significantly in nanocrystalline materials such as quantum dots, owing to their discrete energy levels and enhanced Coulomb interactions. Contrary to this expectation, we demonstrate here that, for a given photon energy, carrier multiplication occurs more efficiently in bulk PbS and PbSe than in quantum dots of the same materials. Measured carrier-multiplication efficiencies in bulk materials are reproduced quantitatively using tight-binding calculations, which indicate that the reduced carrier-multiplication efficiency in quantum dots can be ascribed to the reduced density of states in these structures.
Human rights abuses are increasingly documented through smartphones and personal cameras, generating hundreds of terabytes of digital content from Idlib to Minneapolis. While digital evidence ...provides an important opportunity to democratize the documentation of abuses, the quantity and diversity of this data present challenges for those seeking accountability. Legal advocates must find ways to safely store digital content, parry attempts at manipulation or corruption, and eventually ensure authentication before a court of law. Should litigation arise, the individual who created the digital record is often unreachable or otherwise unavailable to testify, further complicating the underlying legal questions. NGOs and legal advocates have increasingly adopted two new tools - cryptographic hashing and distributed-ledger technology (DLT) - to clear these hurdles. In addition to imbuing civilian-generated evidence with a greater sense of legitimacy and providing immutable protection, these technologies help human rights documentation satisfy US standards for admissibility of evidence. Existing legal scholarship has neither examined these technologies as they relate to US authentication standards nor scrutinized whether they support authentication without witness testimony. There is also a dearth of scholarship that (1) deconstructs and explains these technologies for a legal audience; and (2) provides specific recommendations for courts and litigants. This note fills these gaps by arguing that, with or without witness testimony, these technologies can support the authentication of digital evidence under US statutory and common law requirements. In doing so, it creates a roadmap for how cases that rely on digital evidence can proceed in US courts. Ideally, this roadmap will help to democratize accountability by facilitating new opportunities for justice where admissibility issues previously foreclosed litigation.
Privacy engineering is gaining momentum in industry and academia alike. So far, manifold low-level primitives and higher-level methods and strategies have successfully been established. Still, ...fostering adoption in real-world information systems calls for additional aspects to be consciously considered in research and practice.
Transparency - the provision of information about what personal data is collected for which purposes, how long it is stored, or to which parties it is transferred - is one of the core privacy ...principles underlying regulations such as the GDPR. Technical approaches for implementing transparency in practice are, however, only rarely considered. In this paper, we present a novel approach for doing so in current, RESTful application architectures and in line with prevailing agile and DevOps-driven practices. For this purpose, we introduce 1) a transparency-focused extension of OpenAPI specifications that allows individual service descriptions to be enriched with transparency-related annotations in a bottom-up fashion and 2) a set of higher-order tools for aggregating respective information across multiple, interdependent services and for coherently integrating our approach into automated CI/CD-pipelines. Together, these building blocks pave the way for providing transparency information that is more specific and at the same time better reflects the actual implementation givens within complex service architectures than current, overly broad privacy statements.
Wenn BürgerInnen aktiv am Datengewinnungsprozess als zentralem Baustein empirisch ausgerichteter wissenschaftlicher Projekte teilhaben, kann dies als Beitrag zu einer offenen und bürgernahen ...Wissenschaft angesehen werden. Eine solche Teilhabe kann durch die Bereitstellung von technischen Werkzeugen erheblich erleichtert werden. Daher sollen Participatory Sensing als Bereitstellung von günstigen Sensoren zur Messung von Umweltparametern sowie Wearable Technologies zur Aufnahme von quantifizierten Vitaldaten und physiologischen Zuständen vorgestellt werden. Konzeptionell kann die Bereitstellung von Daten, die mit diesen Werkzeugen erhoben wurden, als Allmende verstanden werden – mit allen damit verbundenen Chancen und Risiken. Nach der Beschreibung von Beispielen aus den Bereichen von Participatory Sensing und Wearable Technologies werden zu erwartende Herausforderungen identifiziert und technisch-organisatorische Ansätze zu deren Lösung skizziert.
A detailed study of the postproduction heat treatment of organic solar cells based on regio-regular poly(3-hexylthiophene) (RR-P3HT) and 6,6-phenyl-C61 butyric acid methyl ester (PCBM) is presented. ...The efficiency of the devices was significantly improved by postproduction heat treatment and both the optimal annealing temperature and optimal annealing time were determined. The phase separation of PCBM and RR-P3HT into bi-continuous network structure occurs within a very short period of time and is very stable.
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